In vitro lymphocyte stimulation with specific antigen in congenital toxoplasmosis.

The development of specific cell mediated immunity was studied in children with congenital toxoplasmosis and the in vitro lymphocyte stimulation test (LST) evaluated as diagnostic test for congenital infection. The test was performed in 35 children, including 5 with a confirmed or suspected congenital toxoplasmosis and for comparison, in 19 dye test positive and 7 negative women. The development of delayed type hypersensitivity (DTH) seemed to follow approximately the same time course in children with congenital toxoplasmosis as in adults with toxoplasmosis. The lymphocyte responses to toxoplasma antigen were low during the first year, but increased markedly during the second and third years after infection. Chemotherapy during the first year of life did not prevent the later development of DTH. It is concluded that a positive LST during the first year of life may be an indication of congenital toxoplasmosis. A negative test is not decisive.